Reproductive efficiency of Thoroughbred and Standardbred horses in north-east Victoria

• Published in: Australian veterinary journal 2010-05, Vol.88 (5), p.169-175
• Main Authors: Nath, L.C, Anderson, G.A, McKinnon, A.O
• Format: Article
• Language: English
• Subjects: animal age; Animal Husbandry - methods; Animals; artificial insemination; breed differences; embryonic loss; farm management; Female; fertility; horses; Horses - physiology; Insemination, Artificial - methods; Insemination, Artificial - veterinary; Male; mares; natural mating; ovulation; Pregnancy; pregnancy rate; reproduction; Reproduction - physiology; reproductive efficiency; Retrospective Studies; stallions; Standardbred; Statistics, Nonparametric; stud management; Thoroughbred; twins; Victoria
• ISSN: 0005-0423; 1751-0813
• DOI: 10.1111/j.1751-0813.2010.00565.x

Objective  To evaluate the reproductive efficiency of horse farms in north‐east Victoria and identify aspects of management to be targeted for improving reproductive efficiency. Design  Retrospective study. Procedure  Records from seven Thoroughbred (TB) and four Standardbred (STB) studs in north‐east Victoria from 1990 to 2001 were reviewed; 8813 cycles in 4455 mares were analysed. TB mares were inseminated by natural mating, whereas STB mares (89%) were artificially inseminated. Results  The overall early pregnancy rate per cycle was 68.8% for TB mares and for STB mares, 68.3%. Multiple pregnancy per cycle was more frequent in TB (8.3%) than in STB (4.6%) mares (P < 0.001). Early embryonic death occurred in 7.1% of TB and 7.5% of STB pregnancies. TB mares had fewer inseminations per cycle (1.03) than STB mares (1.43) (P < 0.001). There was a significantly lower proportion of barren reproductive status within the TB than the STB mares. Pregnancy rate per cycle among stallions ranged from 48% to 79%. Conclusions  On‐farm pregnancy rates in both breeds were higher than previously reported and likely reflect improvements in reproductive management. The disparity between breeds in the inseminations per cycle and proportion of barren mares exposed the differing structures of the two industries, and presents a target for improving the reproductive efficiency in STBs. The difference between breeds in the multiple pregnancy rate per cycle likely reflects the higher ovulation rate of TB mares. The variability in pregnancy rate per cycle between the 22 stallions was associated with differences in individual inherent fertility and the quality of stallion management.